The preparation of a carious lesion for restoration normally requires the use of a dental handpiece burr or other cutting instrument by a dentist. Often the dentist may inadvertently cause positive contact of the dental burr with adjacent healthy tooth structure, causing damage at the surface. As it is accepted that the first step in dental decay is the abrasive one, caused either chemically or mechanically, this accidental damage may well lead to a new carious lesion. In fact, it has been established that between ten and twenty percent of new carious lesions occurring on the interproximal surfaces of teeth are iatrogenic.
Swan-Gett et al. U.S. Pat. No. 3,772,790 issued Nov. 20, 1973, discloses a tooth isolating shield formed by a semi-rigid easily cut covering which is adapted to fit over the upper and lower teeth of the patient, covering the entire mouth area. The shield is then cut by the dentist to expose the teeth or tooth to be worked on. While this shield effectively isolates the tooth or teeth being worked on, keeping the work area uncontaminated and protecting mouth tissue and other teeth from contamination, it does not provide protection from injury to the interproximal surfaces of adjacent teeth as the covering only extends over the labial or buccal, occlusal and lingual surfaces of the adjacent teeth. In addition, as the covering must be formed from easily cut material so that the dentist may readily expose the teeth to be worked on, it obviously cannot afford a high level of protection against injury to the teeth and mouth from inadvertent positive contact with the dental burr or other cutting instruments.